Color separation process and apparatus for the removal of impurities from whole corn kernels



y 1960 F. c. WOHLRABE ErAL 2,9 5

COLOR SEPARATION PROCESS AND APPARATUS FOR THE REMOVAL OF IMPURITIESFROM WHOLE CORN KERNELS Filed Sept. 12, 1958 2 Sheets-Sheet 1 RAW CORNSTORAGE ELEVATOR lmnnxs Flux Chum; Vila. Emu/r51 May 1960, F. c.WOHLRABE ETAL 2,937,750

COLOR SEPARATION PROCESS AND APPARATUS FOR THE REMOVAL OF IMPURITIESFROM WHOLE CQRN KERNELS Filed Sept. 12, 1958 2 Sheets-Sheet 2 Fig. 2

mm: S

United States PatentfO COLOR SEPARATION PROCESS AND APPARATUS FOR THEREMOVAL OF IMPURITIES FROM WHOLE CORN KERNELS Frank c. Wohlrabe andVirgil signors to the United States of by the Secretary of AgricultureFiled Sept. 12, 1958, Ser. N0. 760,818

3 Claims. or. 209-111 (Granted under Title as, US. Code 1952 see. 266

America as represented F. Pfeifer, Peoria, 111., as-

This invention relates to the removal of impurities from whole cornkernels, and has among its objects, the provision of a process whichpermits the removal of rodent excreta pellets from whole corn kernels, acomplete separation that is ditficult or impossible to accomplish byexistingmethods. 1

One object of this invention is to provide a method for detectingthepresence of rat excreta pellets in shelled corn by one or more lightdetecting elements which differentiate between light and dark coloredobjects.

Another important object is to effect the removal of rat excreta pelletsby causing photoelectric cell detector to activate a removal device whenobjects darker in color than corn enter the field of light of saidphotoelectric cells;

Another important object is to remove, by optical detection, the ratexcreta which is of the same size as corn but of variable density andabsorbency which cannot be removed by present pneumatic, sizing, andgravity operations that are now employed in corn milling operations.

Another object of this invention is to provide a method for eleaningcorn to make it more suitable for human consumption.

Another object of this invention is to augment exist-. ing cleaningmethods as a final event in the cleaning process whereby evidence ofcompleteness of removal by preceding processes is obtained.

Another object of this invention is to raise confidence in the purity ofcorn for human consumption beyond that obtainable by existing cleaningprocesses.

Another object of this invention is to combine an inspection process anda separation process in unit appara'tus.

{Still a further object is to provide, for the above process, animproved apparatus which is more efiicient in its components and in thecombination and arrangement thereof.

"To these and other ends the invention resides in certain improvementsand combinations of part and method, which will be hereinafter morefully described and the novel features pointed out in the claims at theend of the specification.

-The methods of cleaning corn for human consumptionused at present byindustry consist of various com- I binations of screening to removecoarse and fine particles; aspiration to remove dust and lightmaterials, and scouringto remove adhering materials. All are aboutZipercentbr less efiicient in their removal of extraneous substancesDepending upon the kinds of screens used iii the screening'proee'ss;practically all of 'themouse pel:

lets and about one-half to three-fourths of the rat pellets are removedduring conventional cleaning.

' According to one method of procedure in the prior art, corn from thescreening process is washed to remove dust, stones and materials of lowdensity, and then dried in centrifuges or screens. About percent or moreof the remaining pellets, which are about the same size as corn kernels,float to the surface and are removed during the washing step.

Another method for further purifying the corn that is practiced in theprior art consists in passing the mixture from the screening proceduresthrough a specific gravity separator operated with air. About 75 percentor more of the pellets remaining after screening are removed by thismethod.

According to another method of procedure in the prior art themixturefrom the screening procedures is passed through precision-sizeseparators of various types. About 75 percent or more of the pelletsremaining after screening are removed by this method.

According to another method of procedure in the prior art;materials oflower or higher density than corn kernels are separated by a combinationof air flotation and gravity flow applied to a vibrating conveyor deck.About 75 percent or more of the pellets remaining after screening areremoved by this method, some in the light fraction, and others in theheavy fraction along with stones present in the feed.

Another method for purifying corn that is practiced in the prior artconsists in passing the mixture from a screening, tempering andconditioning procedure through aseries of electrostatic separators. Areject fraction containing rodent excreta pellets, broken and infestedkernels, insects, worms, foreign seeds, and the like, is separated fromthe bulk of the kernels during passage through an electrostatic field.This procedure has the disadvantage of requiring very high voltages,20,000 to 40,000 volts, erratic performance with feed of variablemoisture content, and a large number of passes to hold the rejectfraction to a reasonable amount.

Another method for sorting solid particulate vegetable matter that ispracticed in the prior art is by means of color. The particles areilluminated as they are individually handled and presented one at a timebefore one or more photocells, and if thecolor does not match thedesired color, the particle is rejected into an off-color fraction. Thisapparatus has the disadvantage of limited capacity-for corn about threebushels per hour per unit, which is about 75 kernels per second. For apractical operation an excessive number of these units would berequired.

Despite the use of various cleaning procedures, rat excreta pellets areoften found in cleaned corn to the extent of one to four pellets perbushel of corn kernels. These pellets are usually within the size andspecific gravity ranges of corn kernels.

We have discovered that color and reflectivity are properties by whichrat excreta pellets consistently differ from corn kernels, and that aseparation can be accomplished on this basis. The electrical response oflight sensitive elements may be used to optically discriminate betweenthe colors of corn and darker rat excreta pellets. The change inelectrical response may be interpreted by a thyratron trigger circuit toinitiate the action of a rat excreta pellet removal device.

We have found that cadmium sulphide photoconductive cells were suitedfor our applications where space was and mirrors could also have beenused to transmit light information to a stationary photomultiplier tubehaving instantaneous response, from the point traversing a scan line,thereby permitting faster scanning rates.

A more practical mass scanner for a moving monolayer of contaminatedshelled corn would be possible by employing a closed circuit televisioncamera as multiple light sensitive elements with provisions foroperation of a rejection device when a pellet is scanned. A belt twofeet wide carrying a compact monolayer of kernels moving at a speed ofone foot per second could carry about 100 bushels per hour.

We have also discovered that a small coating of surface moisture such aswould result from fallout from a water fog enhances contrast betweenlight colored pellets and corn kernels and makes their separationpossible.

Figure 1 is a diagram showing equipment and sequence of operationinvolved in carrying out a preferred embodiment of our invention, and aschematic diagram of an electronic controller that can be used toactivate the rejection device at the correct time and for the properinterval of time.

Figure 2 is a perspective view showing an adaptation ofthe method andapparatus embodying the present invention.

While one embodiment of the invention is illustrated in the abovereferred to drawings, it is to be understood that it is merely for thepurpose of illustration and that various changes in construction may beresorted to in the course of manufacture in order that the invention maybe utilized to the best advantage according to circumstances that mayarise without in any way departing from the spirit and intention of thedevice, which is to be limited only in accordance with the appendedclaims. And while there isstated the primary field of utility of theinvention, it remains obvious that it may be employed in any othercapacity wherein it'may be found applicable.

In the practice of our invention as shown in Figure l, the raw corn isfed from a loading elevator to milling separator of known construction,which removes coarser foreign materials, such as corn cobs, pieces ofwood, stones, etc., dust, lightly adhering solids, and large and smallparticles including some rat and all mouse excreta pellets. The mixturedischarged from this milling operation is then conducted through chute11.

After this preliminary cleaning operation, the mixture may then bepassed directly to devices for efficient rat pellet removal by meanscomprising optical detector activated separation apparatus ashereinafter described.

The mixture is fed to hopper 11 over the vibratory feeder and is spreadout in a layer one kernel deep on the metal vibratory feeder 12. Underthe influence of the oscillatory motion of the pan of the vibratoryfeeder the compact monolayer of mixture is caused to move at a uniformlinear rate so that for an instant each particle of the mixture residesentirely within the boundary of the arcuate scanning zone of Figure 2,and is thus subjected to discrimination between light and dark by meansof light-sensitive element 23.

Said light sensitive element 23, in the preferred embodiment of ourinvention, is shown in Figure 1 as a cadmium sulfide photoconductivecell and is connected through conductors 24 and 25 to electroniccontroller (indicated generally as 39) which impresses a low directcurrent voltage upon said element. The distance between light sensitiveelement 23 and the light reflective object 30 is established by thediameter of the object, the perimeter of the light sensitive element andthe characteristic of the lens 29. In our invention we used a cadmiumsulphide photoconductive cell operating as anon-polar variable resistorthat passed more current as illumination increased The element had aninitial dark resist-. ance in excess of one megohm and a peak spectralre-. sponse at 5100 angstroms. With reference to Figure. 1, optimumperformance with the cadmium sulphide photoconductive cell was obtainedby using a 20x microscopic objective lens 29 to focus on images of cornor excreta 30 with successive full images of each and every particletouching but centered within the inch by inch periphery of thephotosensitive area 23 at some instant during their passage through thescanning zone. Our particular arrangement required an object distance ofinch from the lens and a total distance of l inches between object 30and photosensitive surface 23. A deviation from these conditionsresulted in failure of the particular photocell employed to discriminatebetween corn and equal sized rat excreta pellets. If the image of object30 cast upon photosensitive surface 23 had an area substantially lessthan the area of 23, the electrical response of the element 23 was notsufficient in magnitude to be distinguished from normal background noise(repetitious irregularities in response). Since deep shadows necessarilyoccur at the interstices between contacting kernels of the monolayerpassing through the arcuate scanning zone of Figure 2 greatermagnification of object 30 would also magnify the shadow imageproportionately. With a shadow image substantially covering area 23, theresult was failure of the cell to distinguish between shadows and ratexcreta pellets. The sight of the photosensitive device thereforebecomes a critical aspect of-our invention as will hereafter bedescribed in the claims.

Referring now to Figure 2, the mass scanner of this invention includes aconventional vibratory feeder 12 fed from hopper 11, not shown, avariable speed motor 45 of known construction rotatably connected totransparent scanner disc 46, by means of drive shaft 47, oppo' site endsof which are attached to motor 45 extending into and secured in the hubof flange coupling 48 by means of set screw 50. Flange 48 isconcentrically attached to disc 46 by means of four flat head flangebolts 49, means by which disc 46 is caused to rotate.

Ina perforation within the periphery of disc 46 a light sensitiveelement assembly comprising a 20X microscope objective 29, a tubularbody 28, and a photoconductive surface 23 encapsuled in plastic body 17as shown in Figure 2 is inserted and secured within said perforationthrough disc 46. Plastic counterweight 66 is attached in diametricalopposition to this photocell assembly on disc 46.

In Figures 1 and 2'electrical continuity between lightsensitive element23 and electronic controller 39 is obtained through conductors 67 and 68which are con neeted to brushes 69 and 70, respectively. These brushesare in turn connected to brushes 53 and 54 and lines 24 and 25 throughslip rings 51 and 52, respectively.

Metal slip-rings 51 and 52 are shrunk on each end of cylindricalinsulating body 55. Shaft 47 extends through and is aflixed in the boreof insulating body 55 concentric with the cylindrical periphery ofslip-rings 51 and 52, means by which the slip-rings are caused to rotatewith the disc 46 and shaft 47.

In Figure 2 brushes 53 and 54 are positioned to maintain contact withslip-rings 51 and 52 respectively by attachment to an electricalinsulating structure (not shown) of known material and construction.

Scanning disc 46 is positioned in a plane parallel to and above theplane of vibratory feeder 12 and supported by bolts holding the base ofmotor 45 to a rigid sup Porting structure of known construction.Concentric with and above the circular orbit of photosensitive element28 are located two circular fluorescent light tubes 18 and 18a, 18 beingof smaller radius and 18a of greater radius-than the circular orbit ofelement 28.

. Positioned in.a plane parallel to and below the plane of. vibratoryfeeder pan 12, aretlective screen 63 is ettached to asupportingstructure by conventional means, said screen having sufficientarea to contain the circular orbit of photosensitive element 28.Thelight reflective properties of screen 63 are such that the electricalreenema sponse of light'sensitive elernent 23 is'equal to or exceeds thebrightness response of corn under conditions of.

illumination provided by lamps 18 and 18a, and response remains steadyduring the retrace orbit.

A rectangular opening ,64 in reflecting screen 63 is located within thecircular path of scan and directly below the edge of vibratory feederpan 12 through which the mixture drops to the separation zone. Allsurfaces of vibratory feeder pan 12 visible ;to photoelectric, element23 in its arcuatetravel over .thelip of said pan are coated with acolored material having light reflecting properties equal to or greaterin brightness than the compact monolayer of corn moving across thesurface of said pan.

With pan 1 2 and reflecting screen 63 arranged according to thepreceding specifications and illustration in Figure 2, the surfacevisible to light sensitive element 23 in its circular travel is allequal to or of a higher level of reflectivity than a compact monolayerof corn.

Shaft 57 positioned below and transverse to feeder pan 12, having bothends journaled in a ridged supporting structure, pivotably supportssheet metal deflecting gate 56 by means of integral lugs located at eachend of arcuate deflecting gate 56 which are bent to form right angleswith a chord across the arc of the curved surface to which the sheetmetal gate is formed. Shaft 57 passing through perforation in both lugsis preferentially attached by welding. The radius of the arc to whichthe gate 56 is formed, and of the discharge lip of feeder pan 12,corresponds to radius of the circular orbit traveled by photosensitiveelement 28, thereby obtaining a constant time for a particle of themonolayers movement from the arcuate scanning zone to the separationzone located between the curved edge of the feeder pan 12 and the upperedge of deflecting gate 56 in the reflecting screen opening 64.

Deflecting gate lever 58 is affixed to one end of shaft 57, a pin 61pivotally connects the free end of lever 58 to the lower end of armaturerod 59, thereby enabling solenoid 43 when energized to tilt deflectinggate 56 and divert reject material to the rear side of divider plate 62down reject chute 19 to reject bin 3-2.

With the parts assembled as illustrated and described, the corn cleaningapparatus is mounted on a frame or structure and augments conventionalcleaning equipment. In Figure 1, the power supply provides the necessaryvoltages used in the control circuit 39. When a dark object enters thescanning zone of Figures 1 and 2, the voltage applied to the grid ofThyratron tube 40 causes it to fire and close the single pole doublethrow relay 33. The sensitivity of the controller is determined by thesensitivity adjustment 36. Closing of the single pole relay 33 allowsthe tube 37 to pass increased plate current to the double-poledouble-throw relay 34, but only after a time delay introduced bycondenser 35 and time delay adjustment 42. Closing of the double-poledoublethrow relay 34 allows power to flow to gate solenoid 43 whichtilts deflecting gate 56 so that the dark object and some corn pass toreject bin 32. The length of time during which the deflecting gateremains in the reject position is determined by the adjustment of thehold control 44 of the controller. The plate current to the double-polerelay 34 decreases and allows it to open after the proper hold time. Theplate current of the Thyratron 40 was broken when double-pole relay 34closed so that the controller has now reset and is ready to detect andreject another dark object. Good corn falls in front of deflecting gate56 and chute divider plate 62, down chute 60 to clean corn bin 31.

In Figure 1 a television camera (not shown) may be substituted for thescanning disc assembly as a color discriminating device for a travelingcompact monolayer of corn having a low population of equal sized darkobjects. Said camera is positioned over feeder pan 12 and focused sothat the image of a tranverse line or area of the illumined monolayer ofcorn would exactly span the the deflecting light sensitive surface ofthe television camera. 'By elimination of the blanking'pulse'from thetelevision camera electronic apparatus a signal is obtained when a darkobject 30 enters the sight of the television camera which is used toprovide the voltage to the grid of Thyratron tube 40 of the controlcircuit 39. The resulting chain of events leading to the elimination ofthe dark object from the good corn is the same as heretofore describedfor the scanning disc assembly- Deflecting gate 56 tilts and the darkobject 30 and a smallamount of good corn pass to reject bin 32.

The loss of good corn is further reduced by recycling the first rejectfraction through a second color discrimination cleaning process andcombining the clean corn from it with the clean corn from the firstprocess.

We claim:

1. In an apparatus of the character described means for continuouslydeliveringat a uniform rate a monolayer of a mixture of light and darkobjects to an arcuate inspection zone; a transparent disk rotatablymounted above said inspection zone so as to rotate in a plane parallelto the plane of movement of said mixture of light and dark objects; aplurality of circular illuminating means of different diametersconcentrically mounted above said transparent disk and parallel to theplane thereof; photosensitive means mounted on said transparent diskwith the photosensitive surface disposed in the direction of the movinglight and dark objects and lo- 'cated at such a distance from the centerof rotation of the disk and from the centers of the circularilluminating means as to be on a radius intermediate in length betweenthe longest and shortest radius of the circular illuminating means; anda lens system disposed between the photosensitive means and the plane ofmoving light and dark objects adapted to project an image of a singleobject large enough to fall entirely within the photosensitive area andto touch the perimeter thereof.

2. In an apparatus of the character described means for continuouslydelivering at a uniform rate a monolayer of a mixture of light and darkobjects to a reflective surface in an arcuate inspection zone; atransparent disk rotatably mounted above the reflective surface so as torotate in a plane parallel to said reflective surface and to the planeof movement of said mixture of light and dark objects, said reflectivesurface being adapted to reflect light of intensity at least equal tothat of the light objects; a pair of concentric circular illuminatingmeans of different diameters mounted above said transparent diskconcentric therewith and parallel to the plane thereof; photosensitivemeans mounted on said transparent disk with the photosensitive surfacedisposed in the direction of the moving light and dark objects andlocated at such a distance from the center of rotation of the disk as tobe between said pair of circular illuminating means; and a lens systemdisposed between the photosensitive means and the plane of moving lightand dark objects adapted to project an image of a single object largeenough to fall entirely within the photosensitive area and to touch theperimeter thereof.

3. Color sorting apparatus for separating dark and light objectscomprising means for continuously delivering at a uniform rate amonolayer of a mixture of light and dark objects to a reflective surfacein an arcuate reflecting zone; a transparent disk rotatably mountedabove the reflective surface so as to rotate in a plane parallel to saidreflective surface and to the plane of movement of said mixture of lightand dark objects, said reflective surface being adapted to reflect lightof intensity at least equal to that of the light objects; a pair ofconcentric circular illuminating means of different diameter mountedabove said transparent disk concentric therewith and parallel to theplane thereof; photosensitive means mounted on said transparent diskwith the photosensitive surface disposed in the direction of the movinglight and dark objects and located at such distance from the-center ofrotation of the disk as to be between said pair of circu- '7 larjilluminating means; a lens system disposed betweenthe'phbtosensitive-means and the plane of moving light and dark objectsadapted 'toproject an image of a single object large cnough'to fallentirely within the photosensitive area and to :touchthe perimeterthereof; a Thyratron triggercircuit connected to said photosensitivemeans; discharge means capable of discharging objects in two differentdirections, saiddischargemeans being connected to and being operablebysaid Thyratron trigger circuitto discharge dark objectsin one direction.upon receipt of a dark signal from the photosensitive means and todischarge light objects -in another direction upon receipt of a lightsignal from the photosensitive means, said Thyratron trigger circuitcontaining time delay elements whereby said discharge means-are notactivated until an object has had time to pass from the inspection zoneto the discharge boundary and whereby said discharge means aremaintained open long enough for the object to be ejected from theapparatus.

References Cited in the file of this patent UNITED-STATES PATENTS2,125,639 Maass et al. Aug. 2, 1938 2,701,502 Lukens et a1. Feb. 8, 19552,726,762 Aubry Dec. 13, 1955 2,798,605 Richards July 9, 1957 2,803,161'Summerhayes Aug. 20, 1957 2,881,919 Bartlett Apr. 14, 1959

